According to recent reports, two billion tons of organic waste per year are available on United States farms. These organic wastes can readily be converted to a methane containing gas, or bio-gas, by fermentation of the wastes in a digester. One such process is disclosed in U.S. Pat. No. 3,973,043.
It has been determined that one ton of manure will produce approximately two thousand cubic feet of bio-gas. Therefore, approximately four thousand billion cubic feet of bio-gas could be produced per year in the United States. Since two hundred twenty cubic feet of bio-gas is approximately equivalent to one gallon of gasoline, approximately nine gallons of gasoline could be recovered from one ton of manure, or approximately eighteen billion gallons from two billion tons.
In terms of electrical energy, since twenty cubic feet of bio-gas is approximately equivalent to one Kilo Volt Ampere (K.V.A.), approximately two hundred billion K.V.A.'s could be generated per year.
Obviously, there is great energy generation potential through this type conversion. However, to data the economics of operation to produce bio-gas have not been favorable enough to make bio-gas production readily acceptable. As a consequence, several means for optimizing this type production have been proposed. One such means is disclosed in U.S. Pat. No. 4,100,023. Another is disclosed in the co-pending application of Carter entitled "Improved Bio-Gas Generating Digester," Ser. No. 187,466, filed Sept. 15, 1980.
Accordingly, one object of the present invention is the provision of a more efficient means of producing bio-gas by preventing the loss of bacteria from the digester as sludge is withdrawn therefrom.
Another object of the present invention is the provision of a more efficient means of producing bio-gas by situating bacteria in the zone of the digester where the bacteria will be the most productive.
Still another object of the present invention is the provision of a more efficient means of producing bio-gas by increasing the flow rate of material through the digester.